Distribution of air-fuel mixture in a combustion chamber of an internal combustion engine at the time of ignition closely relates to engine performance and crude pollutant emission, in particular emission of unburned hydrocarbons, carbon monoxide, and particles. Gasoline direct injection provides improved fuel efficiency and high power output. For engines with gasoline direct injection, stratified air-fuel mixture may form at the time of ignition, wherein a richer air-fuel mixture is in proximity to an ignition device. Stratified air-fuel mixture offers thermodynamic advantages in particular in the lower and middle load range, when relatively low amounts of fuel are to be injected.
Different methods may be used to form stratified air-fuel mixture in the combustion chamber. For example, in an air-controlled method, charge is conducted into the combustion chamber forcibly to mix with an injected fuel. Within the combustion chamber, charge movement such as tumble and swirl of the air-fuel mixture may form to accelerate and assist the mixture formation. A tumble is an air vortex about an imaginary axis parallel to the axis of rotation of the crankshaft. A swirl, on the other hand, constitutes an air vortex about an axis runs parallel to the longitudinal axis of the cylinder. A fuel injection jet directed counter to the tumble may distribute the fuel extensively throughout the entire combustion chamber.
The arrangement and the geometry of an intake system of the engine have a significant influence on the charge movement and thus on the air-fuel mixture formation in the combustion chamber. Other attempts to address the charge movement include arranging a pivotable flap or plate within an intake line of the engine. One example approach is shown by Huh et al. in U.S. Pat. No. 6,827,060 B2. Therein, by pivoting the flap attached to the inner wall of the intake line, the fuel-air mixture drawn through the intake line during charge exchange flows predominantly on the side opposite to the flap.
However, the inventors herein have recognized potential issues with such systems. As one example, the adjustment mechanism with the flaps is highly cumbersome and expensive. Moreover, the pivotable flaps may restrict flow and lead to significant pressure drop of charged air flowing through the intake line. Further, soot may accumulate on the flap mechanism and cause malfunction, especially in an engine with exhaust recirculation system.
In one example, the issues described above may be addressed by an adjustable intake line for an engine system, comprising: a first section directly coupled to an inlet opening of an engine cylinder, and a second section mechanically coupled to the first section and pivotable relative to the first section via an actuator. In this way, air-fuel mixture distribution in the combustion chamber may be controlled by pivoting the second section of the intake line relative to the first section of the intake line. Further, wall wetting may be reduced and cooling of the combustion chamber wall may be increased.
As one example, an intake line for conducting charge into a combustion chamber of an engine includes two sections. By adjusting a pivoting angle between the central axis of the first section and the central axis of the second section, turbulence formed in the combustion chamber may be controlled in response to engine operating conditions. As such, charge motion may be specifically adjusted based on the known geometry of the combustion chamber and the condition under which the engine is operating. By controlling charge motion in response to engine operating conditions, reliable combustion may be achieved. By eliminating the flap within the intake line, the adjustable intake line may function more reliable comparing to Huh's intake line. Moreover, the adjustable intake line disclosed herein provides a simple configuration that may easily replace a conventional intake line of an engine system.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.